Scales and Skin
by TheMadKatter13
Summary: John never thought he'd present at all. The few times he'd put thought to it, he'd never thought he'd present omega. And if he'd put any more thought into it past that, he wouldn't have imagined sharing his first heat with a mermaid. Er, merman. Potterlock, merman!Sherlock / omega!John


**I was pointed towards this lovely AUlock exchange (exchangelockDOTtumblr), and I received belislythindor (****belislythindorDOTtumblr****) **as my giftee. They gave me a fantastic list of AUs to work with, and I was more than pleased to be able to combine three of them, one of which I have a great deal of experience in, one of which I have absolute minimal experience in, and one of which I have no experience in fic, but all the experience in source material. The plot (and the length) sorta ran away from me so hopefully giftee enjoys long-ish fics. -.-;

* * *

"I can still smell you, you know."

It was an absolute disservice to his upbringing that John didn't immediately go on the defensive at the stranger's voice. Though, to be fair to the Gryffindor, it was his first time going into heat and he couldn't be bothered with much else besides the roiling need and the gut-wrenching cramps. As it was, he was on his knees, arms wrapped around his stomach and body curled in on itself, his eyes clenched tightly shut and his forehead pressed to December's freezing sands of the lake's shores. The coolness felt absolutely fantastic against the raised temperature of his skin, but it was doing nothing to temper the flames inside him.

"How?" he gasped instead. He'd heard that the pain of an omega's heat was nearly unbearable without the assistance of an alpha('s cock), had even spent plenty of time around unmated omegas in the hospital wing writhing about in pain, but even when his imagination was at its best, it never could have conjured this feeling. The feeling that he needed to be filled was on par with his need to breathe, and it _hurt_.

"A-" John jumped, the waves of pain having completely wiped away any remembrance of another person present"-merperson's biology can smell through the concealing charm you've laid on yourself. Though it really is a rather good one. Certainly its caster would know it was powerful enough to get himself to the hospital wing unmolested? Ah, it's your first heat and you panicked; you thought you were a beta. A seventh year with an aptitude for healer's work should know better, especially a muggle-born with an older sibling." Eyes blinking open in shock at having so many personal details laid out like that, John rocked his head to the side and got his first look at the speaker.

It was a boy. He was being watched by a boy. Well, a teen. A male in any regard, with dark, wet curls and piercing silver eyes set above sharp cheekbones. He was the prettiest boy John had ever seen. And he was laying in the water, legs submerged. Without a shirt.

"Are you insane?!" John gasped, mind temporarily set from his own pain at seeing someone laying in the freezing lake, calm-as-you-please. "What the hell are you doing in there?!"

"I live here," the other replied, tone flat, an unspoken 'Obviously' dripping from every syllable.

"You live-" He stopped mid-sentence at the sight of a large, glimmering, blue-black fish tail waving at him from the water. Right behind the boy. His eyes widened. "You're a mermaid?"

"I believe the term is 'merman'," the boy corrected with a glare. John just blinked at him.

"You can speak English!" He couldn't tell if he was concentrating on the absolute wrong things right now, but he was too startled to really focus on much anything else. The need and the pain took a temporary backseat in his astonishment.

"Of course I can speak English." John wondered if the only tone the boy spoke with was disdain.

"I thought merpeople-" The boy scoffed.

"The others don't care to learn your language. They have no need." He was saved from having to come up with a reply to that by a crippling wave of pain that hit him so hard that his vision went dark. Following that was a wave of heat over his skin and need under that had him whimpering, little puffs of air that scattering the sand in front of his mouth. His robes and his clothes were hot. Too hot. Too scratchy. Their mere existence was painful and before he knew it, he was stripping them from himself, struggling to pull sleeves from arms and trousers from legs without really moving. But when he was finally naked and the cold air provided a comforting blanket over his skin, the millions of grains of sand were just as irritating as the fabric had been. John whined, shifting this way and that, trying to get away from the sensation even though it was impossible.

"What is your name?" The voice was deep, calm, steady. Eyes he hadn't realised he'd closed fluttered open and he turned to look at the merman. Those silver eyes grabbed his own and held them, making him focus on something other than the pain and the need and the sand and the heat.

"Watson," he managed. "John Watson."

"My name is Sherlock, and I need you to listen to me. Can you do that?" He stared at the boy-Sherlock-for a long moment, brain sluggish and needing more time to comprehend than usual. The boy, for his part, just watched him back, those silver eyes piercing him like nothing else ever had. Finally, the words clicked and he nodded. "I can take care of your heat, if that is something you are amenable to."

"How?" John gasped for the second time, trying to keep up with the conversation. He didn't understand...

"Cast a Warming Charm on yourself, John. Then come into the water. The additional heat may feel intolerable currently, but if you do not cast it now, you could suffer hypothermia from prolonged exposure to the lake's temperature." He kept blinking, staring.

"Into the...?" he trailed off, eyes scrunching shut with another wave of pain.

"Do you honestly expect me to come to you?" that sharp voice snapped and John, hit with a wave of heat-induced hormones, flinched. It passed a split second later.

"I'm fucking sorry if I'm not at full capacity right now!" he growled back. Sherlock was quiet for a moment.

"I apologise. Will you come into the water so I may assist you?" The merman's voice was the epitome of polite now, though the dryness spoke to its utter insincerity and John rolled his eyes. Still, the omega grunted an affirmative and began the slow crawl, wincing at each little bit of sand sticking to his skin and wand curled in one hand. When he reached the slight ledge Sherlock was laying on, long-fingered hands pressed against his shoulders, halting him. They were _freezing_, so much so that they broke through the fever-high temperature and sunk to his bones. On reflex, he hissed and pulled back from the touch and then almost fell over at another series of crippling spasms clawing the walls of his uterus. They were increasing in frequency and, logically, he knew that his heat hadn't quite started just yet. But just like the contractions of a birthing, they were a ticking clock, counting down to the onset of delirium rather than relief.

"John," a voice called to him, soft and leading. "John, cast the charm. Hurry." The tip of an icicle traced one cheekbone, pulling him back to himself with a snap and he met Sherlock's patient eyes. "The Warming Charm, John." He nodded and pressed the tip of the wood to the centre of his forehead, and muttering _"Suffio Protego"_ under his breath before feeling a second blanket of heat cover him, though this one was over his skin rather than under it. It was nearly unbearable, just as the other boy had said. This time, when Sherlock's fingers curled around his right wrist, there was only pressure free of that icy chill and he breathed a sigh of relief. If he hadn't been able to tolerate the other's skin temperature, it never would have worked out.

"Good, John. Even in this state, your charms are extraordinarily strong." The fingers tightened and tugged, pulling him back towards the ledge.

"Wait, my wand." The slim bit of wood was pulled from his unresisting fingers and he watched as Sherlock drew it over the ledge and it disappeared beyond his limited view from where he lay on the ground. For all intents and purposes, it appeared as if the merman had dropped it in the water and John gasped in horror, scrambling forward to lean over the small ledge. There was a tiny little cave, more a natural cubby really, right underneath him. It appeared large enough to store his wand in and he breathed a sigh of relief, ignoring the glare of 'What did you believe I was going to do?' he received for his panic.

For a moment he just lay there, unsure where to go next. And then with a roll of silver eyes, long, strong fingers wrapped around his wrists again, dragging him across the sand, ignoring his winces of pain at the grind of grain against his sensitive skin, and finally off the ledge and into the water. Even though the charm was in place, evident by the lack of ice from the merman's touch, he'd still expected the chill of the water to hit him as soon as he was submerged. It never did. Instead, all he could feel was the fire inside him and the warmth outside him as Sherlock's arms wrapped around his waist, pulling him tight against a solid chest and holding him steady. He could feel the gentle sway of the long tail against his legs, the fin far beyond his feet and keeping them both properly afloat. For a moment, it was oddly calming. Just solid arms around him and the easy floatiness of the water. John closed his eyes, dropping his head to Sherlock's neck and wrapping his arms around the others' shoulders. Instinctively, he moved to scent the neck below his lips and though there was something, a muffled strand, he couldn't discern anything more defining than 'water'. The discovery had him startling backwards.

"I don't understand?" The eye rolls were starting to annoy him even in his current state.

"Merpeople do not have secondgenders, John," the merman explained, voice exasperated. "Now, do you want me to help you or not?" John blew air out his nose, bit his lip, and nodded.

The arms at his waist disengaged and he automatically tightened his own arms around Sherlock's shoulders. He knew how to swim perfectly fine, but right now, he knew he wouldn't be able to handle the loss of flesh-on-flesh contact. Or scales-on-flesh, either. Hands wrapped around his thighs, pulling them up and directing them until he understood and wrapped them around a slim waist, locking his ankles together. There didn't appear to be much change in texture where skin turned to scales under his thighs; they both felt as smooth as marble, but there was a definite change in firmness, from the complacent yielding of flesh to the unyielding solidity of scales.

Right when he started to wonder if his slick would be washed away by the lake water or if he would produce it much too fast for that to be an issue, fingers began prodding at his hole, already open and quivering in invitation of any alpha he would have. A shudder ran down his spine at the sensation of penetration, only conducted in curious and rare secrecy in the past, and his arms and legs tightened until he was clinging to the merman like a squid. But it wasn't enough. He needed something longer, something thicker.

"More," he whispered into wet skin, pressing a kiss to the flesh below his lips. "It's not enough, Sherlock."

"I'm quite aware of that, thank you." John could tell that the words came out less biting than they were intended but still biting all the same. "I understand your needs fine. Just because you need 'more' does not mean your body is ready yet. Do you trust me?"

He probably shouldn't say 'yes' because he didn't know the other man-merman-at all but- "Yes."

"Good. Then do be quiet." The Gryffindor in him was well able to stop himself from speaking, but the omega in him was unable to keep his mouth closed, _needing_ something, anything in it like an oral fixation in overdrive. But the only thing he could possible do that with was Sherlock. Without another thought, he dropped down, endeavouring to keep his mouth occupied with the skin in front of him. At first, he was only creating small, little red marks against the pale flesh as a solitary finger worked in and out of him. When a second finger pressed inside him, stretching him but doing nothing to fulfill him, dark bruises bloomed over the small red marks. By the third finger, he could no longer keep quiet. The little whimpers being pulled from his throat were exchanged for muffled cries when his prostate was located and massaged mercilessly. His heat had ramped up his arousal so high that in an embarrassingly short time (seconds), he was coming between them, his cock pulsating where it was trapped between the firmness of their stomachs.

He was panting when he came back from his high, trembling in a way that had nothing to do with the cold air he could no longer feel and everything to do with the merman he was wrapped around. One of Sherlock's hands had found its way into his hair, just cupping the back of his head gently, while the other seemed to be still inside him.

"Thank y-" A wave of cramps stronger than any before swept through his belly and he cried out in surprise and pain, curling further around the firm body between his legs and in his arms. He knew he needed an alpha cock to abate the need, but the calm after the storm had fooled his hopeful mind into believing he could get through it with just fingers. Far from it. In fact, his body only seemed angrier at him for his deception and it made it well known with a rolling wave of convulsions that made him want to sob.

"John, I can fuck you." That deep voice spoke right besides his ear and he moaned at the sound, at hearing coarse language from someone who sounded so posh, the vibrations rippling down his spine and making his entrance feel heated in what he had no doubt was a rush of slick. "If you trust me, I can fuck you through this."

"We don't have any protection," he gasped, even as he angled his hips to try grounding his aching hole against Sherlock's tail which stayed stubbornly too far away for him to do so. It didn't once enter his mind that it was a merman who was offering to take care of him during his heat, the oddity of a cross-species mating escaping him in his need.

"Merpeople cannot impregnate humans, wizard or otherwise, John. I assure you." It could just be a trick. Alphas would say anything to get inside an omega in heat. But then he remembered what Sherlock had said, that merpeople didn't have secondgenders, and omegas could only get pregnant by alphas, and he was nodding his head against the other's neck.

"Okay, yes, please. Fuck. Fuck me, Sherlock," he gasped, his cock already swollen again between them. "I didn't realise how bad it would hurt. Fuck, I never realised." He'd never belittled the omegas he did know about their quarterly functions, but he knew of alphas and betas that did. They thought that going through estrus somehow made omegas weaker. Fuck, if this is what they went through this four times a year, they were stronger than any alpha or beta could ever hope to be.

Something thick was prodding at him, thicker than Sherlock's fingers had been, thicker than his own fingers had been. Instead of the wariness with which he'd approached being penetrated by another in the past, he ground down against it, trying to force it inside to fulfill the need that was utterly ruining him. But suddenly it pulled away and he growled at being denied the relief it promised.

"Damnit Sherlock, just fuck me!" he snapped with a harsh nip of teeth against skin for emphasis. Immediately, the tip of the thickness was back, pressing inside him, stretching him, stretching him so wide and yet... it still wasn't enough. It was only the tip, spreading him and yet, barely filling him. And he _needed_.

He gave one, high-pitched whine, one of need and demand and plea all at once. Then the thickness pounded into him and Sherlock's cock was pressing against his prostate and he was sobbing and clinging as it pulled back out only to slam back in. Again and again it filled him, filled him more than he'd even hoped it would, pressing against his that bundle of nerves with each thrust. A deep voice was murmuring against his ear, a hand was cupping the back of his neck, another hand was wrapping around his cock, stroking it with a gentleness that offset the rough fucking. No, he wasn't just being fucked right now, he was being _dominated_.

And it was _brilliant_.

"Sherlock!" he cried out as his orgasm rose fast in him, not as fast as the first, but it was still already building at the base of his spine, drawing up his bollocks. "You feel- Please don't stop! Fuck, don't stop!" He could feel the _need_ being held at bay by the cock inside him, like every thrust was pushing it back, and if that cock stopped thrusting in, then the need would rush forward and take him over. Despite the violent way he was being taken, their upper bodies did not move and the only sounds around them were that of John's cries and of the nearly-silent tiny waves rippling against their skin.

"John, you're so tight, so hot. You're _burning_ me," was moaned into his ear. The words used and the tone they were used in, the hot breath against his ear, were all just as effective right now as the cock in him was at driving him towards orgasm. "You're so warm, I never want to leave." John just moaned, rotating his hips as best as he could with his legs wrapped around Sherlock's waist. He'd lost his vision entirely and his entire body was shaking and he was no longer holding onto the merman's shoulders, merely draped over them, his entire body devoid of any energy other than what it took to take that cock.

"You're going to make me come, Sherlock!" he gasped. "Fuck me harder. Oh god, _please_, harder!" Even though he needed it, wanted it, he didn't actually expect it to get any better. His mind was already blown away and he was just barely hanging on to his sanity. And then the arms around him tightened, and impossibly, his plea was answered, the cock in him quickening even as it slammed harder and harder against his prostate. "Oh fuck! Fuck fuck fuckfuckfuckfuck, Sherlock!" Orgasm was hanging right on the precipice, but it refused to fall into the chasm and he wanted to sob with the unfairness. "It's not enough! Oh fuck, it's not enough!" he cried despairingly.

Then, more pressed into him, impossibly more, curling up, filling him, filling him right where he needed to be filled, so deep, so deep, so deep inside, a constant, bulbous pressure right against his prostate and he was coming coming coming undone. His sobs of relief and release were muffled by the pale skin of the bony shoulder his teeth were clamped in. Warmth filled his insides and a low baritone vibrated against his ear and his orgasm went on and on and _on_ and it was too much too much _too much_ and he was _still coming_. He blacked out.

When John finally came back to himself, he was trembling in the merman's grasp, full-body trembles that he couldn't seem to stop. The cock inside of him was still fairly thick, somehow a comfort rather than an unwelcome presence, though nowhere near the size it had been when it triggered his orgasm, and Sherlock was whispering in his ear.

"Shhh, it's okay. You're all right. I've got you, I won't let go. Breathe John. Breathe, that's it. Just breathe." Slowly, the tremors faded and he was left a boneless, exhausted lump of human flesh and bones. His arms were hanging like noodles around pale shoulder and his legs were barely floating on either side of the powerful tail, still waving gently to keep them afloat.

"Sherlock," he whispered, voice cracking as it came out. His throat felt absolutely wrecked, as useless as the rest of him, and the rough pants his lungs were still expelling seem to burn along each inhale-exhale.

"You're all right, John. Just breathe, that's it." Sherlock's chest was expanding and constricting in deep, steady movements, like the slow beat of a heart, and the omega concentrated all he could on that, forcing his body to match pace. Finally, finally, he was fully calmed, his body as it was pre-heat, though he could feel another wave simmering in the background, ready to surge again as soon as his body completed its respite.

"That was... brilliant," he breathed into damp skin, somehow not yet dried from being out in the chilly air, the temperature of which he still couldn't feel. The Warming Charm itself would probably end up lasting for a few hours, but he hadn't had to cast that one for some time and he couldn't quite remember its standard duration. As he just lay there, he realised Sherlock had said nothing and he tensed.

He thought he'd felt- But... "Did you-"

"Yes, John, I did." The other boy's voice was steady, but husky, and John pulled back as best as he could to look the merman in the face. High cheekbones were still as pale as when he'd first laid eyes on them and at first he worried that Sherlock was unaffected, and then he realised the silver of those bright eyes were nothing more than a thin ring around blown pupils.

"That... was okay then? For you?" he pressed tentatively. Even though Sherlock had been the one to offer, the Gryffindor was worried that somehow the pheromones of his heat had influenced the query. As a healer and a muggle-born who grew up in a world without magic or alphas and omegas, consent during such times as heat and rut were always forefront in his mind, and he was just as aware that it could go both ways: that an omega could be taken against their will and an alpha could take against _their_ will. And if he'd just made a new friend, a new brilliant, fantastic, impossible friend, he didn't want to lose him.

Sherlock's lips quirked and he blinked, eyes becoming mischievous. "Mmm, yes, it was satisfactory."

John blinked backed at him for a moment before he began to laugh. "You utter cock. It was fantastic for you too and you know it." In the next second, his mouth was being devoured, his breathy laughs being licked away by an insistent tongue. The taste of Sherlock wasn't something he'd thought about, and yet, it wasn't what he expected either. Well, perhaps he expected something a bit... briny. Fishy. It was nothing of the sort. He was warm, a bit sweet, musky. His tongue dominated the omega's mouth, exploring, overwhelming, and all John could do was hold on for the ride, feeling like he was being swept away by the tide. When Sherlock finally pulled back, they were both panting and John felt a bit dizzy.

"I didn't think alphas and omegas kissed?" he gasped, recalling his lessons on the matter. Sherlock's lips quirked and something unreadable passed through his eyes in a flash.

"Did you already forget what I said about merpeople, John?" the merman asked, cocking an eyebrow. With a mock glare, John darted forward for a quick nip against those plush lips.

"Heat, remember?" he retorted.

"Even for a Gryffindor, I expected better from you," the other continued. John gave a mock gasp and then began to laugh. And then stopped, frowning.

"Wait... How did you know I was a Gryffindor?" And then he remembered what the other had said before his heat started, facts about his life as a muggle-born and his magical aptitude laid bare barely a few words into their acquaintance. "How did you know all that... stuff about me?"

"Simple. I observed. This is not the first time you've walked around the lake and you're always wearing your house scarf when you do. Easy enough. Your aptitude for charms is quite clear with the ease and strength of the concealing charm you placed on yourself when you realised your heat was starting. As for your healer's work, also easy: you were able to quickly diagnose your symptoms and act accordingly, something even a wizard-born would not do unless they'd seen a heat start in person. Unless you have great deal of friends who are omegas and you've been present for most of their presentations, you have spent a great deal of time in the hospital wing. Hence, healer or healer apprentice. Additionally, though you appear to be a seventh year, you were obviously surprised by your own presentation, which you would not have been had you been wizard-born and grown up with the expectation that you would present alpha or omega. Therefore, muggle-born, and expecting to remain a beta as your parents were and as a small percentage of muggle-borns and squibs are. As for your sibling, your robes are second-hand, but they're newer than to belong to a parent. Older sibling."

John could only stare in surprise. "Brilliant."

Sherlock blinked back. "Really?"

"Yes, of course it was." How could he not believe him? It all sounded so simple laid out like that, but that just simply wasn't how people thought, wizards or muggles. No one John had ever known or heard about possessed the ability to take in those small little facts and put it all together in such a way. It really was quite... brilliant.

"That's... not what people normally say." Sherlock turned his head away and if John didn't know better, and he really shouldn't as he'd only just met the man, he'd say Sherlock was embarrassed.

"What do they normally say?"

"Piss off."

John's clear, surprised laugh echoed across the lake and the merman just stared at him for a moment before joining with his own quiet laughter.

**.oOo.**

John almost didn't realise when the next wave of his heat started, he was so absorbed in Sherlock's explanations and lectures of the lake's contents. He had never realised what all was down there, the things that were hidden in its depths. He knew the squid lived there, but he never knew it had a mate and a child. He knew there were other merfolk, but he'd no idea they had villages and pets. The merman had additionally found more discarded wizarding tidbits than he should have been about to count and yet he remembered it all (all 394 tidbits) and his eyes lit up as he listed them to John and explained the sorts of experiments that he'd conducted on them.

The Gryffindor had already been amazed by the kinds of deductions the merman could make, but the more he talked, the more John realised exactly _how brilliant_ Sherlock actually was and he was free with his praise as he took it all in. The genius would startle from his speech with each one, blinking before looking away in a manner that made the omega think that if those pale cheeks could flush, they would.

At one point, so caught up in his lecture, Sherlock had said, "I would love to take you down when you're not in heat so I can show you!"

"I'd really like that," John had replied automatically, honestly and earnestly. The wizard had laughed at the merman's expression, leaning forward to press a kiss to those plush lips automatically. And then he realised what he'd done without permission, without his heat or the immediate aftermath of it as an influence and drew back quickly, face flushing with his embarrassment as he turned it away to carefully study the opposite shore. Firm fingers slid up his neck to curl around his jaw and turn his head back to Sherlock's and next thing he knew, he was being snogged senseless. And not long later, his heat had risen again and the merman had lifted him to lay on his belly on the ledge he himself had been laying on earlier. As soon as he was settled, arse and legs still submerged, a firm torso draped over his back, forced him to stillness as that delicious cock from before prodded at his hole from behind.

He wished he could feel the merman's warmth across his back, but just his presence, the touch of flesh from waist to shoulder, the smooth scales against his arse and thighs, was enough to satisfy the omega's need for skin-on-skin contact. Hands circled his wrists, pulling them out in front of him and stretching his arms and his torso along the sand until they could go no further. Elongated in such a way, he felt so very vulnerable under the other's dominant ministrations, and it only heightened the pleasure of the slow way he was entered. This round, though the heat burned at him, killing him so sweetly, Sherlock never sped up, no matter how much he cried-pleaded-begged. Each thrust was firm-hard-full-filling, but not quick, never quick.

The omega's erection was pressed into the cool earth of the ledge, left unattended entirely, and no amount of tugging at the fingers around his wrists gave him leave. He was sobbing by the time that brilliant cock coiled inside him, that same unrelenting press to his prostate, and he was coming without a single bit of pressure against his cock. Sherlock's teeth embedded in his shoulder this time, far away from his scent gland as the merman came inside him, the heat that flooded his insides dampening the need that would rule him four times a year and the soft litany of "John John John" in his ear making his heart clench painfully.

When his mind returned from him from its orgasmic state, he could feel a bodily exhaustion tugging at his eyelids and he was pretty sure he slurred when he informed the other boy of the fact. Strong, iron arms lifted him from the sand, hands brushing granules from his skin as he was lowered back into the water, held aloft by those same arms. He was unconscious before he'd even been settled.

**.oOo.**

As the waves of his heat ebbed and flowed over the hours, Sherlock was there for each one, coaxing him through it with a low baritone and long fingers and a clever tongue and a thick cock. Every time the Warming Charm began to fade and the Gryffindor began to tremble with cold rather than pleasure, sometimes even before, the merman was holding his wand and reminding him to renew the spell. Sometimes he just put the wand in the omega's hand, wrapping his own larger one around it and pressing the tip of the wood back to John's forehead, whispering the spell in his ear until the wizard parroted it. Every time the omega fell asleep, it was in Sherlock's arms and every time he would wake up, they would be in a different part of the lake and he would have new facts to be taught and to learn. All in all, for all that it was spent with a stranger, and a merman at that, John thought that there wasn't a better way he could have spent his first heat.

At some point in those four days, he'd managed to fall in love with the genius though he was careful to never voice it, even in his weakest moments, and he would always fall into sleep smiling at the sight of Sherlock's soft, shy smile. Which was why he nearly fell into a full-blown omega panic when he woke up dry, wrapped tightly in sheets from shoulder to toe rather than pale arms around his waist and surrounded by the quiet bustle of the hospital wing rather than the cool stillness of the lake.

"Woah, John! Calm down mate, you're safe. Do you know where you are?" Eyes wide and breathing harsh, he tried to scramble from the not-Sherlock voice, but the sheets over him were too tight, too restricting and it only heightened his panic. Mind still caught up in heat-instincts of the last few days, he oscillated between distressed whimpers when fabric failed to give way and growls accompanied by bared and snapping teeth when hands not-Sherlock's attempted to still him. Suddenly, a wave of cool calm swept over him like a dive into the lake and he stilled, his head floating in the unexpected haze.

"Watson," a new voice said. It still wasn't Sherlock, but whatever influence held him now pushed his panic to the background. "Watson, look at me, there's a good lad." His head flopped to the side and the vague form at his side cleared into one he knew well, a matronly older woman with a kind face. "Do you know who I am?"

"Madame Pomfrey," he murmured, tongue thick in his mouth.

"Good lad. Do you know where you are?" he stared at her for a moment longer before taking in the things he could see around her without moving his head. Cots and partitions met his eyes and he blinked, trying to place it all.

"Hospital wing," he managed after a minute.

"Very good. And do you know what happened?"

Sherlock. Sherlock happened. Beautiful, brilliant Sherlock. But he didn't want to share the merman with anyone. He was John's. So instead he just said, "Presented omega."

"That's right. Now, you just kip here, get your energy back," she instructed firmly. "Lestrade here has been nice enough to keep you company during your stay so you best visit with him before curfew. I won't be far, understand?" It took a second to realise the last bit wasn't directed at him and he lolled his head the other way to find Greg seated on his other side, nodding solemnly.

"Understood, Madame Pomfrey," the seventh year said, and John thought for a moment that he was going to salute the witch. But the moment passed and she was bustling on and his fellow Gryffindor was leaning forward with his elbows braced on his knees. "You okay?"

Head still fuzzy, John frowned. 'Okay'? He felt deliciously shagged out and bereft at the loss of his mate's presen-er, not his mate, Sherlock-Sherlock's presence. He was without the merman, back in the castle, and he had no clue if the would be able to see the boy again, or even if he wanted to see John again. Why would he be okay with that? "Why wouldn't I be okay?"

Greg's face went slack. "Why wouldn't-? John! They found you naked and laying half in the lake, unconscious and apparently in the middle of your first-" The alpha stopped abruptly, cheeks flushing. "_Your first heat_," he hissed lowly, eyes darting around. "They had to strap you to the bed and spell you into sleeping for three days until your heat passed!" Only one part of that sentence really stuck.

"Three days? I was still in heat for three days after they found me?"

"Yes! And they didn't even realise you didn't make the Hogwarts Express until your mum sent an owl the next morning! John, do you understand the kind of danger you were in? You were missing for four days! Dumbledore himself had to be called in and he was the one who found you!"

_"If you trust me, I can fuck you through this."_

John _had_ trusted, he'd trusted Sherlock to do exactly that, and yet the merman had surrendered him halfway through his first heat. Why? John didn't expect the other to have fallen in love with him like he had with the genius, after all, he was about as average as one could get, but he'd thought that there had perhaps been camaraderie, if not friendship. And yet Sherlock had let him be taken, let him writhe out the rest of his heat alone, unconscious, and bound. His stomach churned and he frowned deeply.

"John?"

"Mr Lestrade?" John's head jerked up at the old voice, one he'd heard in the Great Hall many times over the past years, but had never really been that close to its owner.

"Professor Dumbledore!" Greg almost tripped somehow standing up from his chair and he might've laughed if he'd been in any better a mood.

"I would like a word with Mr Watson, if that's all right?"

"Of course! I'll just, um. John, I'll see you later?" the alpha stuttered out, half-bowing at the headmaster even as he stumbled even more trying to leave. Dumbledore waited until the seventh year left before taking the recently-vacated seat and holding out something small and yellow.

"Sherbert lemon?" he offered, face blank but eyes kind. The omega attempted a smile.

"Thank you, professor," he accepted, popping the treat into his mouth. There was a long moment of silence as they just sat there, regarding each other, letting the sweets dissolve slowly on their tongues. John's was a mere sliver before the older omega spoke again.

"Your first heat took you by a bit of a surprise, I gather?" The Gryffindor flushed and nodded.

"Yeah, I kinda thought after all this time I was... well, a beta." He really should have known better and his lack of forethought on the matter just made his embarrassment hike, even through the calming spell. Still, he only received an understanding smile.

"I didn't get my first heat until I was nearly nineteen," the older omega imparted and John blinked in surprise.

"Really?"

"Really. I had thought I was a beta like my brother." The headmaster had a brother? He'd never even heard... "I was visiting the Minister at the Ministry when it came over me." John winced sympathetically, but the headmaster just shook his head. "It turned out all right. I had a friend who was willing to help without requiring a bonding of me." John's mind flashed back to Sherlock, the conversations they'd managed to have in between and the relationship he thought they'd built. He would have gladly bonded with the merman had it been offered. But it hadn't been, and furthermore, merpeople couldn't bond anyway, the thought of which sparked a lament without end deep in his chest. "It seems you had a friend who was able to help you through as well." Now he did flush, the heat in his face so strong he could feel it travel up to his ears and down his neck as he gave one, short nod.

There was silence after that for a long moment as he stared at the bustle around them. And then he realised he might be required to respond and his head shot up to find Dumbledore watching him patiently. He opened his mouth to speak but nothing came out and he wouldn't have known what to say anyway. The headmaster smiled at him suddenly and his breath caught in his throat.

"New friends in curious places are always interesting, Mr Watson." John could only nod in silent agreement as the headmaster gifted him a second sherbert lemon and then he was gone. Left alone, the Gryffindor laid back down, and thought.

**.oOo.**

It took John almost a week before he gathered up the courage to even leave the castle (What if Sherlock didn't ever want to see him again? What if he'd let the professors take him, because he'd tired of John?), but the day before the new semester started, he found himself out the doors, down the grounds, and ambling slowly around the edges of the lake. Three circuits later, he came to a standstill where his heat had hit him and he just stood there, staring at the unrippled water. A minute later, he was skipping stones along the smooth surface and picking the smoothest, flatest projectiles from the ground under his feet for use in his own poor amusement.

"John?" The rock in his hand flew in completely the wrong direction and his spares fumbled free of suddenly-clumsy fingers.

The face he had fallen in love with was staring at him from over _that_ ledge, the one Sherlock had hidden his wand in, the one he'd been taken against so firmly that second wave. The rest of the merman, however, was nowhere in sight.

He didn't say anything, not sure where he was supposed to start. Not sure where he _wanted_ to start. Just as those plush lips opened again, he blurted out "Why did you give me up?" And then promptly flushed. He hated that he even had that reaction: blushing. If anything, he'd always thought that he might have presented alpha like Harry had. His personality matched well enough. That he had presented _omega_ was just as much of a shock as him presenting at all. That he'd had so many omega-like reactions since presenting, so unlike _him_, irked him to no end, but there was nothing he could do to stop them.

"I didn't want to." He jerked back, surprised from his thoughts by the quiet but firm voice.

"What?" John blurted, startled by the response. Sherlock frowned. The Gryffindor knew he hated to repeat himself, but more often than not, he would, if John asked.

"I didn't want to give you back," he reiterated. Now the Gryffindor's anger and embarrassment were fading, only to be replaced with confusion.

"Then why did you?"

"Dumbledore made me." If the wizard didn't know any better, he'd say the merman was pouti-

"Wait _what_?" he exclaimed. There was an explosive sigh and then pale arms made and appearance to push a pale torso out of the water and up onto the ledge, that gorgeous blue-black tail he hadn't seen much of during his heat making an appearance to slap the water's surface with an annoyed flick, not unlike a twitch of a cat's tail. The marks John had made along the smooth column of a long neck and across bony shoulders and over the broad plane of an upper chest still hadn't healed and stood out, stark and possessive, against such pale flesh. Even in his current mood, it was an arousing sight.

"I was content to stay in this spot with you. It has adequate cover should anyone venture nearby, and decent seating for some positions I desired to try with you." The admission had his face in flames and all moisture evaporating from his mouth. "But then the professors began to search for you the second morning and I was not going to let them take you from me." As much as those words sounded _right_ to the omega, something about them felt _off_ to the Gryffindor. "So whenever we were in danger of being discovered, I would move you while you rested."

"You would-?! Sherlock!" he exclaimed, flabberghasted by the boy's single-mindedness and inconsideration. "I was missing for _four days_! My own family didn't even know where I was! I was supposed to have gone home on the Hogwarts Express for break! I _told_ you about my father! I _told_ you how he went to work one day and never came home! Why would you make my mum go through that again? Why didn't you just tell them I'd chosen you?" As calmly as he'd tried to start the conversation, he was shouting by the end, cheeks flushed in anger rather than arousal now.

"Because you trusted your first heat to me!" the merman shouted back, startling John who'd never once heard his friend even raise his voice. Not even during one of his moments of clarity between waves of need when he'd realised how fast and how far he'd fallen and he'd abandoned Sherlock to frolic in the open waters and the merman had been calling after him to come back, frustration and annoyance clear in his voice when the omega had refused to listen. "Because I told you I would fuck you through it!" There was something... something... building in the air the more heated the other spoke, and it was making his head feel light and his knees feel weak. He wavered where he stood, pressing a palm to his forehead, trying to stall the way everything around him had started to spin, but Sherlock seemed too incensed to notice as he continued. "Because they would have taken you from me, just like they did anyway!" Glowing silver eyes swam in his suddenly hazy vision and the air was suddenly a bit too thin and his lungs seemed to fight for every breath. Something in the air... "Because as soon as you let me touch you, you were _mine!_" the alpha roared and John collapsed to his knees.

All that separated the omega from the _thing_ swelling in the air between him and his friend had been a thin, tenuous layer of _something else_, and with Sherlock's last words, it popped. His body, which had been preparing itself eagerly for whatever was inside, began to scream and rail at the utter _emptiness_ it was met with, like a burst balloon full of nothing but hot air. He felt... blank beyond a hollow echo of an unfamiliar need and despair that seemed the to thrum soul-deep inside the fragile shell of his skin. There was a strange, high-pitched keening sound in the air, and after a moment, it dawned on him that the sound was coming from him.

There was a low murmuring above him and pressure on his wrists and sand on his cheek and the world was still spinning even as he was pulled into the cold water and into strong arms, his nose placed against a damp neck.

"I'm sorry, John. I'm so sorry, I didn't know that would happen. I'm so sorry." The omega, overwhelmed and floating, body numb from omega-instinct overload and the chilling water, closed his eyes and breathed in deeply, trying to find his alpha's scent. There was nothing. Only the scent of the lake. And that strange muffled chord that no amount of scenting seemed to draw out . He whined again, drawing his nose up and down the neck in front of him, trying to find a strong enough source to the scent. "Shhh... You won't find anything, John. I'm so sorry. I didn't mean to- I would never- Please, just breathe. Close your eyes and breathe."

He did as the other directed, becoming a bundle of cold, sogging rags in strong arms as he let all tension go from his limbs. And the longer he lay there, the more the strange backlash from _the thing_ from before faded, letting strength return to his limbs and logic to his mind, even as he began to shiver from the cold water. Several minutes later, he was still held tightly in Sherlock's arms, even though all his faculties had returned, and his face was bright red as a result.

"If I may continue?" a dry voice asked directly by his ear. A shiver ran down his spine at the proximity of that baritone and its hot breath and he struggled to get free of the arms he wanted nothing more than to wrap himself back up in. He completely forgot he was still wearing any kind of clothing, unlike the several days of nude freedom of his heat, and as soon as pale fingers released him, he found himself kicking twice as hard to get absolutely no where. Just as he began to sink, the merman wrapped those same torturous fingers under his bicep, pulling him back up and back into his arms. Panting from the effort, John just nodded his head and kept his chin hooked over the naked shoulder to avoid eye contact after his embarrassing attempt at escape.

"Thank you." Immediately, he tensed at the gratitude, another thing he'd learned was rare for the merman, but his response was ignored for elaboration. "I was able to keep us from the professors for four days. But then they brought in Dumbledore and that man is not as stupid as the rest of them." High praise indeed from the scornful teen that had him raising an eyebrow in surprise. "He found us, made me give you to him. I couldn't- I'm not strong enough to combat him yet normally, much less attempting to do so like I am now." John frowned at the odd wording, but before he could get any clarification, one arm released him and a hand smoothed up his neck to cup his jaw, turning his face towards Sherlock's. "Please believe me, John, that when I say I wanted nothing less than to give you to anyone else, I mean it."

He couldn't seem to break his eyes away from the serious, silver gaze, and slowly he nodded. "I believe you, Sherlock," he whispered. Those glowing eyes remained fixed on him for a just a little longer before the glow faded and the shoulders under his hands loosened. In that second, the Gryffindor realised his friend had been as worried about their continued relationship as he had, and clearly one of them needed to say something to make it understood that everything was all right. He had his wand with him. He knew how to cast a Warming Spell, which he really should cast now if he didn't want to spend the next few hours combating hypothermia, he knew how to cast a Bubble Head charm. He had his new friend at his side, looking adorably uncomfortable and awkward. What more could he really hope for with all that was available to him in the moment?

"So, what's this you wanted to show me in the lake then? I believe the words you used were: 'Could be dangerous?'"

**.oOo.**

As the next few weeks passed, John attended his classes, he did his homework, he worked his arse off during Quidditch practices and games, he studied his arse off for his coming NEWTS, and he kept his eye out for whatever was attacking the muggle-borns. And every spare second was spent at Sherlock's side in the lake.

He met the squid and its family, with which Sherlock seemed to have formed some sort of rudimentary sign language combined with speech on the merman's half. He was taken to the village of merman, and he hadn't really thought about it before, but his friend looked absolutely _nothing_ like the merpeople he'd studied in books or the ones he met: the other merpeople had greenish skin, somewhat fish-like faces, sharp teeth, and webbing between their fingers. Sherlock looked more like the muggle's imagining of the aquatic race, half boy and half fish. But as he was guided to the lake's floor to scrounge and scavenge with his best friend, the strange differences were lost in the excitement of the things they found half buried sand and the glowing look he received when they did. And sometimes, if another student was on the grounds and walking around the lake, they would find a hiding spot nearby and Sherlock would whisper deduction after deduction into John's ear, accompanied by a breathy chorus of "Brilliant!" or "Amazing!" or any variation thereof.

The remains of winter passed quickly in that manner and spring was attempting a breakthrough when John realised his second heat was just three weeks out. After a solid five days of internal debates, occasionally manifested in angry little grumbles to Greg's apparent combined amusement and confusion, he decided to ask Sherlock if the merman wanted to help him through this heat as well, even though neither of them had brought up his first one or the possessive claims that had followed. But the silver looks he still got, the way the merman seemed to curl around him when they spied on students from the lake, the the arm that never left his waist when they went to the mer-village, spoke plenty. It took three more days to muster the courage to ask, but when he went down to the lake twelve days before his second heat, his friend wasn't there waiting for him like usual.

"Sherlock?" he called over the water from the ledge where it all started. Silence and stillness. "Sherlock!" he called again, a bit louder. Still, nothing. On occasion, the genius would get caught up in some experiment or another at the bottom of the lake, and John would have to go fetch him, only to be berated for going about the lake alone minutes later. Sighing in annoyance, the Gryffindor stripped and stored his clothes, casting the Warming and Bubble Head Charms as he prepared himself for another 'safety lecture' before diving into the water. A few minutes later, he was frowning in confusion at the place Sherlock normally was that he currently wasn't. He thought about going to where the merman slept and then realised he'd never been shown to it, if the git even had one in the first place.

Huffing into the bubble, the omega swam to the squid, intent on finding his missing friend. He wasn't actually sure if the squid understood English, but he asked "Sherlock?" anyway as he mimed out the merman's tail. Great eyes stared back at him, and then a tentacle pointed in the direction of the mer-village. Biting his tongue, John shook his head and tried to think of a different way to explain who he was looking for as the squid's mate joined it. Eyes widening with the sudden idea, John pointed at the mate then patted his chest before miming the tail again. The squid seemed to puff a little in recognition before pointing towards the surface.

"He's not up there, I looked," he said automatically. The squid jabbed upwards more pointedly and John barely resisted trying to massage the bridge of his nose, mainly because the bubble was in the way more than he didn't want to appear rude. The squid began pointing almost violently at the surface and the wizard held up both hands. "Yes! Okay! I understand he's at the surface!" But he didn't understand at all. He'd already called out for the other boy, and the merman had always appeared after, but maybe he was caught in his mind palace? With another deep sigh, he saluted the squid and returned to the surface to swim around the edges in search of his absent merman.

An hour later, he had swum around the entirety of the lake, checked every miniature peninsula and exposed cave. When none of them turned up his merman, he growled and, renewing his Warming and Bubble Head spells, dove right back down towards the mer-village. Though they understood what he wanted faster than the squid did, they were no more help than it had been, pointing towards the surface with fingers and weapons. He wanted to hurt something with the strength of his frustration, and he was in a foul mood by the term he emerged from the lake. Said mood lasted all the way through dinner and John was so snappish with his responses to any question or comment that even Greg was avoiding him by curfew. After the next day's bout of fruitless searching, and the one after that, and the one after that, his mood was so foul that Peeves started following him around whenever the poltergeist saw him in the halls, creating sparks of fake lightning above the Gryffindor's head and banging pots next to his ears and pouring water over him.

After a full week with no sign of Sherlock and no results in his search efforts, he began to despair that maybe the merman had grown tired of him, was hiding from him and employing his cohabitants to misdirect the wizard at every turn. Absolutely dejected, in the last four days before his heat started, he stayed inside the castle and surrounded himself with his friends... and received more offers of heat-service than he could count. Despite his loss of Sherlock, both as a friend and as a heat partner (_'Mate,'_ his mind whispered treacherously), he felt no inclination to let anyone near him during his heat, no matter how much he would hurt during his physical denial. He could already feel the effects building up just one day before: a bodily exhaustion, increased libido, nose extra-sensitive to the scent of alphas around him.

Most of his fellow Gryffindor and Slytherin seventh years were already waiting outside the Defense Against the Dark Arts classroom when he arrived, walking slow from the onset of heat symptoms (exhaustion, increased libido, heightened sense of smell) plaguing him as his body ramped up for the start sometime in the morning. To his surprise, everyone already there was whispering to one another and it was clear it wasn't just another piece of gossip.

"What'd Lockhart do this time?" he asked as he approached Greg and the others, adjusting his bookbag strap for the twentieth time in as many minutes; his skin was itching under his robes and he longed to get to the point where he could just take everything off. Their completely-barmy DADA professor was well known for the shenanigans he got up to and sometimes John couldn't help but wonder why the headmaster had hired the looney in the first place.

"Not Lockhart," the alpha corrected, "Holmes!" Holmes. That sounded somewhat familiar but it wasn't really ringing any bells.

"Holmes? Who's that?" He shifted his bag again, eyes tightening in his annoyance.

"You know that fifth year who tried to transfigure himself last year and got stuck? They actually got him undone!" the alpha exclaimed, bouncing on the balls of his feet as if he'd been the one to do it. John wracked his memory. That kind of thing was big, even for wizarding school, as far as he understood. He himself had considered becoming an Animagus, but he wasn't quite confident enough in his magical or personal strength to be sure he would even succeed. Apparently this fifth year hadn't had the same forethought.

"Yeah, I don't remember that." Greg's mouth opened as he frowned, and then it closed with a snap, face taking on a contemplative look.

"You know, I think that was when that bludger got you in the head and you spent that week in the hospital wing," the Gryffindor mused. Oh yes, that. John remembered that. Well, he didn't actually _remember_ most of that, but he remembered that it happened to him. A delicious scent suddenly filtered down the hallway but before he could track its source, the corridor around him went silent.

"Merlin's beard," someone whispered.

"Holy shit," Greg gasped at his side. "That's him. That's the kid." Frowning in curiosity, John turned and had enough time to see dark curls, pale skin, sharp cheekbones, grey eyes, and a Ravenclaw house scarf before he was pressed into the stone wall by a tall form, long fingers hard around his waist and a nose against his neck, that delicious scent thick around him.

"Hello, John." Everything about the person against him was familiar, from the facial features to the hands that held him tight to the deep voice, but he'd never encountered them in the castle. He began to feel faint, wondering if he'd somehow fallen into a dream, or even a hallucination incited by his omega biology missing the last person it mated with during such times.

"Oi!" A loud shout pierced the air, echoing in the corridor, startling John so bad that his head jerked back and slammed into the stone and he let out a hiss of pain as he saw starbursts behind his eyes. "Get off of him!" Greg shouted. The body in front of him moved to the side and he found his fellow seventh years all posed with their wands out, looking as if they had no qualms in using them. And John knew they would. The Slytherins were just staring in unabashed curiosity but they didn't look inclined to help out one direction or another. "Who the hell do you think you are?!"

"Sherlock Holmes," the boy replied, as if that said everything. To the others, 'Holmes' just meant, apparently, that kid who failed to transfigure himself and just got turned back. But to John, 'Sherlock' meant everything he'd fallen in love with in the past three months. It meant a blue-black tail and sneaking out of the castle at midnight and eye-twinkling discoveries. It meant sweet kisses and strong arms and a thick cock. He moaned, slick rushing from him and a fire igniting under his skin. Pheromones exploded in the air, first his own, and then from every alpha around him, so suddenly that it made him dizzy and his knees gave out and he fell back against the wall behind him. That long body was immediately in front of him again, though this time it was facing his house-mates, right arm held out and wand in hand.

"Mine," a familiar baritone growled. Just as quickly, more growls joined and John could just barely see Greg from around the black robes, teeth bared. He really hoped Greg didn't want to mount him because he much rathered it would be Sherlock.

"Not a fucking chance," the Gryffindor across from him growled back. All he could smell was pheromones, possessive and challenging, and when he felt another gush of slick, he realised his heat must have started early, triggered by the arrival of his chosen alpha and excess of alphas around him reacting to his heat-scent. "Get away from him or I'll make you get away from him."

"Try," Sherlock challenged. He could see long fingers tightening around a wand and his friend's mouth opening and he couldn't think of anything he could do stop it and-

"What do you think you're doing?!" a new voice exclaimed, halting but not lessening the tension in the corridor.

"Professor McGonagall!" several voices chorused in surprise, several wands hurriedly disappearing into robes simultaneously. However, neither Sherlock's nor Greg's followed suit.

"Mr Lestrade, I am surprised at you! The Head Boy duelling in the hallway?" Across from him, his friend's face flushed and his wand arm lowering. The alpha in front of him, however, kept it resolutely where it was. "And Mr Holmes! Five minutes out of the hospital wing and you're already causing trouble! I'm well aware of your disdain for the rules, but this is a bit much!" Sherlock didn't move and the professor frowned. The fact that anyone would disobey the elder alpha at all would later shock John at the memory, but it was at that moment that his body chose to cramp and scream at him and he curled in on himself, breathing a low groan into his robes.

"Now what is going on here?" the professor repeated, face turning as she met each of their eyes in turn, though she hadn't yet spotted John from his spot on the ground, half hidden behind Sherlock.

"This alpha," Greg spat, "showed up out of nowhere, molested John, and triggered his heat a day early!" the Gryffindor exclaimed, pointing at where the omega was curled on the floor. The professor turned and started at the sight of him, her hand flying to her chest.

"Mr Watson!" she cried, starting towards him only to stop when Sherlock shifted with a growl. For a moment, she just blinked at him in utter surprise. After all, who was stupid enough to challenge a teacher? "Right then. Mr Holmes, you'll be going to the headmaster as soon as I get Mr Watson to the hospital wing."

"You will not touch my omega," the alpha snarled from above him.

"He is not _yours_!" Greg rejoined exasperatedly, throwing his hands up in the air. As another familiar wave of need and pain washed through him, John decided this really was not the time for discussion. His biology had needs and his alpha had come to take care of them.

He reached a hand out, curling his fingers in the black cloth of Sherlock's robes. "My alpha," he called, tugging. Immediately, he was the centre of everyone's attention again.

"John, you've never even met the bloke!" Normally, he'd thank Greg for always being on the lookout for him, but right now, John wanted to Stupefy the cockblock.

"I assure you I have," he ground out, resisting the urge to grind his arse against the hard stone. It would only heighten his need, and right now, that was the last thing he needed with this battle of wills in front of him and half his year-mates around him. "He spent countless hours fucking me through my last heat and I'd appreciate it if he wasn't prevented from doing it again." A stunned silence greeted his declaration, Greg and Professor McGonagall staring at him in shock, most of the Gryffindors the same, and the Slytherins looking like they were only a bucket of popcorn away from a real good piece of entertainment.

John tugged on the robes in his hand again and this time, their owner followed his silent command and turned to crouch low in front of him, bringing a sorely missed face into view. "You'd better have a damn good explanation and a damn good nest for me," he growled through teeth shut in pain. He was treated to one of Sherlock's rare warm smiles and he couldn't help but attempt a smile in return.

"I do," he was assured, the normally deep voice made deeper by the same arousal blowing silver-ringed pupils wide.

"It's not in the lake, is it?" he asked suspiciously. And as nice as the lake had been, a bed would be infinitely better. Sherlock chuckled, shaking his head.

"No, it is not in the lake."

"Good."

"Can you stand?"

"It'll be messy if I try," he chuckled breathily. Sherlock leaned forward and looped one arm under his knees and the other around his shoulders, lifting him bodily into the air. John made a noise of surprise and arousal at the display of strength, slinging his own arms around the alpha's neck (oh, the alpha scent was _lovely_ and it was _everywhere_), and letting himself become comfortable in the familiar arms. Slick was flowing generously from his hole now, caused by alpha's actions and pheromones. The arms didn't feel as steel-strong as they had when the wizard had been a mermaid, but there was strength in them none-the-less. The alpha strode through the crowd of staring Gryffindors and Slytherins towards Professor McGonagall, who was watching them with eyes just as wide as her students, hand still on her chest.

"Well," she hummed. And then another moment later, "Well," again. "If that is the case, I will escort you to the mating ward in the hospital wing," she said, beginning to walk away.

"That is not the room I require," Sherlock said, and the other woman stopped, turning back to him with a raised eyebrow while John looked on with confusion as a silent conversation seemed to occur between the two alphas.

"Of course, Mr Holmes. Nothing usual will do for you, will it?" Her tone was dry and despite his lack of understanding regarding the topic, her last words rang true enough to John.

"Usual is boring," the Ravenclaw scoffed, his fingers tightening around John as he strode away towards the closest staircase. John had no clue where they were going but he was content to wait, the alpha's mere presence enough to assure him that he would be taken care of during his heat. More than that, as Sherlock started climbing the stairs, the first wave of cramps swept through his uterus and he groaned, crumpling in on himself. The arms under him shifted, and he found his nose pressed against skin, against the source of the amazing scent. He stayed that way until they passed, nuzzling at his alpha's scent gland. This. This is the scent he'd been missing every time he'd attempted to scent the merman before. By the time the pain passed, they were already on the stairs between the sixth and seventh floors.

"Ask your questions now," Sherlock instructed, startling him from his biology-induced silence. "You won't be able to soon and I suspect you very much wish to know." At the thought of why he wouldn't be able to ask soon, John flushed and was suddenly very glad his face was still pressed to Sherlock's neck.

"So, not a mermaid then?" For some reason, though he'd long gotten used to the feeling of the other teen's arms around him, somehow it felt different now, with Sherlock carrying him over land rather than through water. He walked with a smooth gait, nothing but grace and strength despite his burden. Need pulsed through him and he licked a smooth stripe up the pale neck. The smooth gait stuttered for a step and he smiled, pleased with the reaction.

"Far from it," Sherlock replied stiffly. "An overconfident wizard, nothing more. A Ravenclaw who didn't believe one couldn't complete an Animagus transformation into a fantastic beast."

"You utter git!" John laughed. "That's one of the very first things you learn not to do!" The alpha shrugged as he stepped onto the seventh floor, pace quickening once he was back on flat ground.

"I had convinced myself that I could learn from their failures. That I was stronger and smarter than they were," the teen explained. John couldn't stop laughing now, leaning back in the embrace keeping him aloft. Sherlock's cheeks were red though his expression was bland as he walked purposefully towards the giant tapestry of Barnaby the Barmy trying to teach trolls how to dance ballet. As they approached however, the tapestry melted away, leaving only a stone wall with a wood, green door on which was a brass '221' and a matching doorknocker. It looked like... a muggle's flat door?

"What the hell is that?"

"That is the door to my flat in London," he said as it swung open as they got closer, revealing a cluttered by homey looking sitting room. "And this is my flat."

"How the hell is your flat in the castle?!" True, John was a muggle-born who'd adapted to the wizarding world like a fish to water, but some things still caught him by surprise, and this was one of them. Enough so that the next throb of his oncoming heat went by completely ignored.

"Don't be an idiot, John," Sherlock scoffed as he strode through the sitting room and to another door that opened for them, revealing a clean bedroom that felt baren when compared with the sitting room. "We're in the Room of Requirement and as I currently require a bedroom, preferably one already thick with my scent," oh, it was thick with his scent alright-the delicious scent of Sherlock was _everywhere_, "the Room produces a simulacrum of my flat."

John was still absolutely lost. He'd never even heard of the Room of Requirement, but the alpha was sitting him on the bed and working rather intently on removing all of his clothes, giving him no time to think. In seconds, John's heated skin was completely bared to the cool air and he gave a sigh of relief. Just as his own hands reached out to the other's robes, he was pushed onto his back and distracted with soft lips and a sweet tongue sweeping into his mouth as long-fingered hands stroked down his torso, making the muscles in his stomach quiver. He was panting and dazed when the Ravenclaw pulled away but there was no respite as the lips merely moved down his chin to his neck, nipping at his scent gland. A by-now familiar pulse of _need_ and _empty_ hit him at feel of teeth over such an intimate spot and he moaned, rolling his hips and fingers digging into Sherlock's shoulders.

"Oh god, Sherlock," he groaned as a hot mouth sucked a temporary mark into his neck and fingers curled around his ribs. John's hips bucking up and meeting unhelpful black cloth rather than the alpha himself. He whined low in his throat, pushing at Sherlock's shoulders, trying to make him back off so John could just _catch his breath_. Instead, that mouth abandoned his scent gland to move down his chest, teeth and tongue paying too much attention to the lines of his muscles and bones and his nipples and his belly button. Then the omega cried out as his cock was engulfed in the wet heat of that same mouth. So engrossed with the use of that tongue against his slit and around his glans, he didn't realise one hand had left his side until two fingers slid into his already-drenched hole. He cried out, bucking up into the mouth only to thrust his hips back down onto those extraordinary fingers, caught between the two pleasures and unable to pick which he wanted to enforce. Lucky for him, he didn't need to pick because no matter which way his hips went, Sherlock followed.

"Please! Oh god, please!" he begged, curling his own fingers into his hair, pulling at the short strands as his eyes clenched shut at the pleasure, feeling orgasm pooling low in his belly. "Sherlock! Shit!" he cursed as the enthusiastic mouth only increased its intentions to bring him off. He was writhing in place as a third finger pressed inside him, right against his prostate. It only took that one touch before he was crying out his release into Sherlock's mouth. His heartbeat was pulsing heavily in his cock as he was sucked and fingered through his orgasm.

When he was finally released, his breathing was ragged in his chest and his heat was once again raging at him for having an orgasm without being stuffed with a cock. But Sherlock's mouth was still around him and Sherlock's fingers were still in him and Sherlock was all around him and SherlockSherlockSherlock. Slowly, the heat and the fingers pulled away, drawing a high whine from his throat as they went. The form between his legs also pulled away and he blinked open his eyes to see the Ravenclaw standing besides the bed, staring at him. John rolled limply toward him and reached out to tug the scarf free, pulling it towards himself and draping the knitting across his nose, breathing in the scent. It was thick, but faded, and he imagined it's lack of wear from Sherlock's time as a merman was at fault.

"I want to see you," he said, eyes fixed on Sherlock's and voice muffled from being covered by the scarf. The alpha's eyes widened and he licked his lips as his Adam's apple moved in his throat, but he nodded and began to strip. Slowly. Agonizingly slow. John groaned in frustration and squirmed, dragging the scarf down his body and smearing the alpha's diluted scent into his skin.

"John," the Ravenclaw breathed, emitting palatable clouds of pheromones. Finally, all clothing was gone and he got his first look at the other teen's legs, and more importantly (for the moment): his cock.

"You really are an alpha," the omega appraised, attention riveted to the long, thick, erect piece of flesh and it's slightly swollen base, the knot that would be inside him shortly. He licked his lips.

Sherlock cleared his throat and John was quite pleased to find that Sherlock could not only blush, but could do so quite profusely. "Yes, well, ahem, that's..." Something tickled at his mind and he frowned, trying to track it. Suddenly, it dawned on him.

"You're an alpha," he said, feeling a bit stunned at the utter realisation of it and all of its implications occurring to him at once. Like an eruption of fireworks in his mind. He wondered if that's how Sherlock felt when a grouping of deductions came together.

The Ravenclaw frowned. "Yes, John. I do believe that was just established." The Gryffindor rolled his eyes at the 'obviously' tone he'd gotten so used to the last few months.

"No, I mean, there's always been something about you that was there but wasn't there," he tried to elaborate, thinking of the way he always felt like Sherlock scent was empty, the oddly alpha-like exclamations he'd been treated to, that odd moment when he'd confronted the merman about hiding him from the teachers, that thing that had swelled between them like an explosion of pheromones but with nothing behind it. "That's it, isn't it? Whenever you talked about your biology, you always said 'merpeople biology'. You never said anything about yours. You were still an alpha, just in the wrong body, weren't you?" The look he received was so proud it made him blush harder than the lewd looks he'd gotten earlier.

"Correct, John. It hadn't been an issue until you. I was content to be as I was as there were plenty of experiments to conduct on what was in the lake. But then you came along. Wandering around the lake with your friends. A Gryffindor, but not like the rest of them. At the time, you intrigued me, which is more than I can see for the majority of homosapien. I watched you whenever you walked around the lake. And then your heat started and I could still smell it so clearly even though my biology couldn't react. I could smell you from the cave I slept in, John." The alpha's eyes were practically glowing again and John swallowed hard at the thought of his heat-scent drawing the merman to the surface from the depths of the lake.

"You gave your heat to me, and even though I wasn't quite an alpha, I was able to satisfy you. Quite thoroughly. And as much as your biology had taken over you, you were still intelligent, quick, strong. Instead of being able to solve you, you only became more of a mystery. Did you know you're the first to do that, John? That you're the first human, wizard or muggle, to capture my attention and keep it? To raise more questions than are answered?" Dazed by the alpha's words, he could only shake his head. Compliments from Sherlock were rare, and to have so many lobbied at him made him feel as if... as if... it was... indescribable. The alpha began to prowl back to him, climbing slowly onto the bed and crawling towards him in such a way that made him feel as if he were about to be devoured. His heart raced in his chest and he couldn't breathe, couldn't move. He could only watch.

"I want to keep you John. I want you to be mine when we leave Hogwarts. I want to bring you to my flat in London-I told Mycroft to make sure it was kept as I left it. I want to solve crimes with you, once I get it out that I'm not dead-most of my clients must have thought as much when I didn't come home last summer but it'll pick up again when there's a good murder." Wait. One of those was not quite like the others.

"Crimes?" he asked, brow dipping in his confusion. "Murder?" Sherlock grinned, shifting John's thighs apart to settle on his knees between them.

"I'm a consulting detective. Only one in the world. I created the job my first summer break." John didn't know how to reply to that but of course the vain git would create his own profession and of course he would have done it so young. "More importantly than that though, I am an alpha, and you are an omega, and I want to impale you with my cock and sink my teeth into your scent gland." All breath he had managed to keep in his lungs left him in a rush. "I want to make you mine in a way everyone can see and no one can deny or argue."

"Oh," John said. He felt dizzy and overwhelmed and why did Sherlock always have to say _just the right thing?_ The alpha was staring at him and waiting for a response of some kind, but all he could say was "Oh" again. But that in itself seemed to be answer for his genius because Sherlock was grinning _that_ grin again and leaning forward, cock nudging at his now-drenched entrance and tongue probing between his lips.

His alpha's mouth was still occupying his when he finally slid inside and _oh Goooood._ His jaw dropped and his head fell back and it was so _different_ than when he'd been a merman. Somehow, it was longer and thicker and it was like he could feel every vein and every beat of the Ravenclaw's pulse inside him and he _wasn't moving_ and-

_"John,"_ Sherlock breathed against his jaw, forehead pressed to his cheek. "How can you be so much hotter than when we were in the lake? So much tighter. I can feel how wet you are. Merlin, you're _drenching me_." The alpha was pressed against him, from his arse to his shoulder and his cock was throbbing between their stomachs. It felt better than anything he'd ever felt before; better than receiving his letter or his wand or casting his first spell or flying for the first time or sex for the first time or sex with Sherlock for the first time or _anything_.

And then Sherlock moved.

_"Fuck!"_ He knew logically that he had a vaginal opening inside his anus, but to _feel_ the alpha's cock in there was just better than he could have ever hoped for, better than he could have imagined. Every thrust of Sherlock's was slow and deep and his alpha just _wouldn't stop mouthing at his scent gland_, ramping his heat higher and higher. His skin was burning inside and out and he didn't think he'd stopped moaning. He was getting dizzy from being unable to draw a proper breath, but he couldn't be arsed to care. Every time that cock pulled away, the needy emptiness rushed forward, and every time that cock pressed back in so sweet and slow, it pushed that feeling away.

There was something thicker pressing against him now, stretching his hole even wider each time Sherlock fucked into him and he moaned, swiveling his hips up and wrapping his arms tightly around his alpha's back. He was sure he was scoring that pale back with his nails, leaving bright red trails that he could admire later. But as Sherlock's arms wrapped around his back, hands gripping alternate shoulder from behind and the alpha's fingernails digging into his skin, he could only grip tighter, claw harder.

Orgasm was threatening each time he was filled, the knot getting so large it could no longer fit properly, his bollocks drawing up tight, and he had no doubt Sherlock's were the same. His alpha's mouth was sucking marks into his neck, stinging pleasurably with teeth and soothing after with tongue. The friction against his cock was becoming slick with the sweat between them, and he wantedneeded a hand to touch him to help him get there but he didn't want to let go of Sherlock and he didn't want Sherlock to let go of him but it didn't matter because he was so close he was so close so close close-

"Sherlock, oh god, please. Please!" he cried, startling himself by breaking the long silence in the quiet room.

"I know, John. You're almost there," was whispered against his skin. He felt like sobbing because he felt _there now_.

"I'm there, Sherlock!" he cried. "Please, your knot!"

"Shhh... Shhh..." was not what he wanted to hear but it was what he got as his mouth was was taken over, that stupid tongue keeping him from speaking and he was going to asphyxiate. He couldn't _breathe_ and his orgasm was risingrisingrising-he wrenched his head to the side "SHERLOCK!" Orgasm rushed out his cock and he could feel his passage convulsing rhythmically around his alpha's cock. And then Sherlock was shoving his knot into him and sinking his teeth into his scent gland and his orgasm renewed, spreading through him like lightning and turning his vision white as his alpha's cock swelled against his prostate and his come filled him (full, so full), soothing his heat.

John was sobbing into Sherlock's shoulder when his mind came back to him, soft words murmured into his ear as soothing fingers carded through his hair. His heart was pounding through his chest at a pace that should concern the healer side of him and his breath was coming out in fast, heavy pants. But all he could think about was the fact that he was mated to the person he loved and that that person's cock was still pulsing inside of him. All he could smell was the scent of their mating, the way their individual scents were now laced with each other's. Sherlock's cocked throbbed hard and he moaned weakly at the sensation of it, the way his muscles fluttered around him, milking him, and a gentle wave of electricity buzzed in his veins.

"You're all right, John. Just breathe." He could only nod, still dazed, still trying to recover, head falling back against the pillows, eyes wide but unseeing, fixed on the ceiling. A smooth, wet tongue continued to lathe over the new wound that was his mating mark. It felt deep, but then, it had to be to reach the scent gland properly so that it could soak in the alpha's saliva and take in his scent, declaring him as Sherlock's. The thought made him moan again. It was all he wanted in life since his first heat, the other teen becoming his mate. And now he had it. He was almost afraid to fall asleep, that he would wake up alone in his dorm in the Gryffindor tower and this had all been a dream. But every throb of pain in his neck, every miniscule thrust of Sherlock's hips when the alpha came again, the tight grip on his shoulders, were constant reminders that this was real.

Finally, the alpha's knot went down but Sherlock didn't move. The weight and warmth over him over John, between his legs and in his arms, was infinitely comforting in the ebb of his heat. He had zero desire to move and he really hoped Sherlock felt the same. But then the alpha began to roll away and he whined, clutching tightly at him. A deep chuckle reached his ear and he immediately recoiled, withdrawing his hands as if his mate was made of hot coals.

"No, shhh John. It's all right. I'm not leaving. I promise." Cautiously, he tilted his head back down, finding silver eyes smiling down at him, a soft, gentle expression on Sherlock's face he'd never seen before. Slowly, the alpha leaned down, drawing him into a soft kiss, drawing his sudden heat-induced insecurity from him like poison from a wound. This time when he pulled away, John tensed slightly but stayed silent, waiting. Sherlock simply rolled to the side, tugging at the blankets until he could get them out from under them. His alpha settled the coverings over them and then tugged and maneuvered John until the omega was curled into his chest, nose against his scent gland. The scent was more potent than ever before, right from the source and he hummed in satisfaction. Somehow, the first round of this heat was more tiring than that of his first heat, and he felt his eyes drooping against his best efforts.

"Go to sleep John. I'll still be here when you wake up. I'm not leaving." After a moment, John relaxed into his mate. His _mate_. It felt strange, in the best way, to think that. But he wanted to say it.

"My mate," he said slowly, as if savouring the feel of it on his tongue, as he nuzzled at his alpha's scent gland. Sherlock's reaction was instantaneous. Every line in his body stiffened and against John's thigh, he felt the thick length of a cock hardening. A surprised noise erupted from his throat.

"Say that again." The Ravenclaw's voice was hoarse, odd considering the calm way he'd spoken a moment before. The Gryffindor grinned against the pale skin.

"My mate." There was a growl from his alpha and a flurry of blankets as he was rolled onto his stomach, Sherlock himself taking the place of the sheets across his back. Already the erection was full and leaking as it pressed between his cheeks, small movements of Sherlock's hips dragging the length of that brilliant cock along his tender hole, making him moan as he shifted his arms, folding them under his head.

"I thought you wanted me to sleep," he murmured into the crook of his elbow. A moment later, the glans caught on his rim and his mate slid inside with a thrillingly breathy, low moan right against the shell of his ear. He had to bite his lip at the auditory proof of how much his body affected his genius mate, well aware of the whimper that threatened to escape his own throat at the sensation of his alpha filling him again, .

"I changed my mind." The alpha's cock was pulled from him before it was thrust back in, the pace noticeably quicker than the last time. It remained so as his mate continued to fuck him, not once letting his chest separate from John's back. Teeth and tongue worried at his fresh mating mark and the omega was sure it would be constantly renewed throughout his heat. A hard thrust right against his prostate had him seeing stars as the teeth nipped their way up to his ear, pulling the lobe of his ear into a hot mouth. "Say it again."

FIN

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**Well. Ahem. belislythindor, I really hope you liked, and I hope everyone else liked it too. Thanks go to shjw* (shjwwriterscircleDOTtumblr) for reading over and making sure this wasn't just rife with plotholes. Please don't forget to review, and come by and see me on tumblr (themadkatter13-fanfictionDOTtumblr). :3**


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